The present invention relates to a multi-layer film structure comprised of an inner sealing layer, an outer layer and a core sandwiched between the sealing layer and the outer layer, and wherein the film structure is particularly for use in a high-speed pouch forming, filling and sealing machine.
Traditionally, in North America, the film used for packaging fluid milk or the like in flexible plastic pouches consists of a 76 microns mono-layer polyethylene film.
However, this standard film has some disadvantages which should be overcome. For example, the packaging operation requires a certain amount of electrical energy for the heat sealing operation due to the thickness of the film. To generate this heat electrical energy is dispensed. It is desirable to develop a process which could decrease the energy consumption in order to make the operation more economically feasible. Another problem involved with the sealing operation is that some of the hardware, such as the sealing element per se and the rubber and Teflon(trademark) parts associated with the sealing jaws have a relatively short useful life, requiring frequent changes and again increasing the cost of producing milk pouches.
Yet another problem resulting from the packaging of liquids with a mono-layer polyethylene film is the amount of waste and machine downtime due to film roll changes and seal breaks. Packaging milk or other liquids with mono-layer polyethylene also involves the use of a narrow sealing window which renders the operation somewhat difficult. Finally, the seals obtained with this type of film pouches, often exhibits weakness which can cause fluid leakage.
Polymer film pouches made from a polyethylene film structure and used for packaging flowable materials such as milk, are known and examples of such are described in U.S. Pat. Nos. 5,288,531; 5,360,648; 5,364,486 and 5,508,051, all of which have issued to the Dow Chemical Company.
It is a feature of the present invention to provide a thinner multi-layer co-extruded film structure, which overcomes some or all of the disadvantages of the prior art and incorporated in a bag forming, sealing and filling machine to improve on its method of operation and throughput.
It is another feature of the present invention to provide fluid containing pouches that exhibit desirable properties as compared to the pouches of the prior art.
It is another feature of the invention to provide a multi-layer film structure which makes it possible to reduce the material used as compared to the film of the prior art.
It is another feature of the present invention to provide a multi-layer film structure for packaging liquid that can be sealed at much lower seal initiation temperature.
It is another feature of the present invention to provide a multi-layer film structure for packaging liquid that has a greater machine direction tensile strength.
It is another feature of the present invention to provide a pouch made with the multi-layer film structure according to the invention that is improved in horizontal seal strength, exhibits lower horizontal seal thinning, and minimizes post consumer waste.
It is yet another feature of the present invention to provide a lower gauge pouch having a higher stiffness enabling pouring of liquid, and which exhibits a substantial improvement in drop test performance and puncture resistance.
It is another feature of the present invention to provide a multi-layer film structure for packaging liquid into pouches, which ensures a reduction of the electrical energy required for sealing due to lower heat initiation temperature and lower mass to be sealed.
It is another feature of the present invention to provide a multi-layer film structure for packaging consumable liquid products into pouches which uses lower sealing temperature and thereby improves the useful life of the jaw sealers, such as the rubber, and electrical sealing heads, and resulting in overall energy reduction.
It is another feature of the present invention to provide a multi-layer film structure for packaging dairy products into pouches that permits a substantial reduction of wastes and downtime caused by film roll changes.
It is another feature of the present invention to provide a multi-layer film structure for packaging liquid wherein sealing is easier to operate due to a wider sealing window, and speed increase is made possible as a result of a faster sealing cycle.
According to another feature of the present invention there is provided a high-speed pouch forming, sealing and filling machine and its method of operation and utilizing sealing heads which operate at lower temperatures due to a decrease in the film thickness as compared with 76 microns mono-layer polyethylene film and thereby resulting in an electrical energy saving and wherein the thin film permits the machine to obtain a substantially higher yield with a film roll substantially the same size as with the 76 microns film.
According to the above features, from a broad aspect, the present invention provides a multi-layer structure for use in packaging consumable liquid into flexible pouches comprising an inner sealing layer, an outer layer, and a core sandwiched between said sealing layer and said outer layer, wherein the sealing layer comprises about 70 to 95 weight percent of a metallocene catalyzed resin having a density of between about 0.902 and 0.912, and about 0 to 60 weight percent of a low density polyethylene or a mixture of low density polyethylene and linear low density polyethylene, the outer layer comprises a low density polyethylene or a mixture of low density polyethylene and linear low density polyethylene, the core comprising a mixture of about 10 to 90 weight percent of a polypropylene copolymer and about 10 to 90 weight percent of a low density polyethylene or a mixture of low density polyethylene and linear low density polyethylene, said multi-layer structure having a thickness within a range between about 50 and 70 microns. The metallocene catalyzed resin is m-polyethylene.
According to a still further broad aspect of the present invention there is provided a high-speed pouch forming, sealing and filling machine which comprises means to draw a multi-layer film from a film roll over a pouch-former to form a plastic film tube having an overlap vertical film edge. A vertical sealer is provided and has a sealing head for heat fusing the overlap vertical film edge to form a vertical seal. A filler tube extends into the plastic film tube for injecting a consumable liquid product at a filling location of the plastic film tube. A horizontal sealing jaw, having an electrical thermal sealing element, is provided for effecting a horizontal seal across the plastic film tube and spaced below the filling location and for simultaneously severing the tube to form a top transverse seal for a filled pouch and a bottom transverse seal for a pouch being filled. The multi-layer film has an inner sealing layer, an outer layer and a core sandwiched therebetween. The characteristics of this film are described above. The horizontal and vertical seals have an improved seal strength of 30% to 50% as compared with the 76 microns mono-layer polyethylene film and a 10xc2x0 C. to 15xc2x0 C. reduction in seal initiation temperature, an improved machine direction tensile strength of 25% to 40% and an improvement of 30% to 50% in puncture resistance, while reducing the sealing cycle time and increasing the throughput of the machine.